Ruby delete method (string manipulation)

Question

I'm new to Ruby, and have been working my way through Mr Neighborly's Humble Little Ruby Guide. There have been a few typos in the code examples along the way, but I've always managed to work out what's wrong and subsequently fix it - until now!

This is really basic, but I can't get the following example to work on Mac OS X (Snow Leopard):

gone = "Got gone fool!"
puts "Original: " + gone
gone.delete!("o", "r-v")
puts "deleted: " + gone

Output I'm expecting is:

Original: Got gone fool!
deleted: G gne fl!

Output I actually get is:

Original: Got gone fool!
deleted: Got gone fool!

The delete! method doesn't seem to have had any effect.

Can anyone shed any light on what's going wrong here? :-\

score 13 · Accepted Answer · answered Apr 25 '10 at 10:11

13

The String.delete method (Documented here) treats its arguments as arrays and then deletes characters based upon the intersection of its arrays.

The intersection of 2 arrays is all characters that are common to both arrays. So your original delete of gone.delete!("o", "r-v") would become

gone.delete ['o'] & ['r','s','t','u','v']

There are no characters present in both arrays so the deletion would get an empty array, hence no characters are deleted.

answered Apr 25 '10 at 10:11

Steve Weet

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Another typo chalked up to the examples in the book then. ;-) Thanks a lot for the explanation. – Brian Apr 25 '10 at 17:52

score 2 · Answer 2 · answered Apr 25 '10 at 07:46

2

I changed

gone.delete!("o", "r-v")

to

gone.delete!("or-v")

and it works fine.

answered Apr 25 '10 at 07:46

Sid Heroor

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Thanks a lot! I tried just about everything but that! Out of interest, are you on MAC OS X, too? – Brian Apr 25 '10 at 08:13
Nope. I use ruby on windows and linux. Most of ruby should be OS agnostic and so any initial problems you face shouldn't be specific to OS X. – Sid Heroor Apr 26 '10 at 02:25
Careful about expansion when using double quotes : http://stackoverflow.com/a/4190812/1729094 – yPhil Oct 22 '15 at 18:26

score 1 · Answer 3 · answered Apr 25 '10 at 07:25

1

You get same o/p using some different way like gsub

puts "deleted: " + gone.gsub('o', '')

o/p

deleted: Got gone fool!

answered Apr 25 '10 at 07:25

Salil

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Strange, isn't it? Are you on MAC OS X, too? – Brian Apr 25 '10 at 08:13

Ruby delete method (string manipulation)

3 Answers3